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It is well known that counter-propagation of structured light fields allows shaping of three-dimensional (3D) structures in amplitude, phase, or polarization. Here, we numerically demonstrate the potential of implementing non-diffracting Bessel–Gaussian (BG) beams for advancing this approach by taking advantage of its characteristic propagation behavior. In this context, we investigate the self-healing property in this counter-propagating configuration, observing a spin angular momentum (SAM) variation and the formation of a continuous orbital angular momentum (OAM) gradient in longitudinal direction. Additionally, by counter-propagation of BG beams of different types, namely, scalar and vector BG beams, we are able to increase the complexity of accessible 3D structured fields, revealing combined amplitude, phase, and polarization modulation in all spatial dimensions. Thereby, the SAM and OAM of the input light fields can be used to design the resulting 3D structure and its angular momenta. The presented light fields open new possibilities for customized optical trapping potentials and allow new insights into fundamental spin–orbit interaction in counter-propagating superpositions of structured fields.

We transfer on-demand structuring of three-dimensional scalar amplitude and phase patterns to polarization-structured, vectorial light fields and its singularities. Our approach allows inheriting non-diffracting as well as self-imaging propagation properties to tailored singular ellipse fields, including self-replicating amplitude, polarization, and singularity configurations. It is experimentally realized by amplitude, phase and polarization modulation of the angular spectrum of the light field. We demonstrate the customization of complex singularity formations embedded in three-dimensionally (3d) tailored vectorial field. Our findings show that embedded networks of polarization singularities can be customized to propagate in a robust way along curved trajectories, creating and annihilating during propagation. This 3d structuring of vectorial singular light fields opens new perspectives for in-depth singularity studies and for advancing applications as optical micro-manipulation and material machining.

The biomimetic, deterministic aperiodic golden angle Vogel spiral lacks both translational and rotational symmetry and exhibits circularly symmetric scattering rings in Fourier space. We present a versatile and low cost method for maskless fabrication of a Vogel spiral relief grating by illumination of a photoresist with laser light complexly structured using a spatial light modulator and subsequent transfer of its negative into a polymer layer via replica molding. We investigate its diffractive properties and present as one application its implementation as a surface structure, leading to an efficiency enhancement of 18% in an organic solar cell.

Aberrations of light are commonly known as undesired effects in different applications, including optical trapping. However, here we demonstrate how to take advantage of controlled spherical aberration in order to shape extended optical trapping landscapes, fully-structured in three-dimensional (3D) space and embedding transverse as well as longitudinal electric field contributions. We numerically analyze the light field customization by the simple means of including glass plates in a counter-propagating trapping configuration, presenting sculpted intensity as well as 3D polarization ellipse structures. Experimentally, we prove the realized counter-propagating optical structure by particle velocimetry as well as the analysis of scattered light of optically guided micro-particles. Finally, we demonstrate the potential of our approach by creating extended 3D particle assemblies.

Beneath being a well-established tool in optical manipulation for spinning and eventually sorting trapped objects, transverse energy flow (TEF) of light represents a versatile, illustrative and instructive approach to understand singular light fields and their properties. Up to now, these transverse flows were mainly investigated in its orbital part, for example, as in optical vortices, whereas the study of complex spin flow density (SFD) topologies has not yet reached the same mature state. Especially, the defined customization of energy flow and respective SFD fields has not yet been initiated. By the application of higher-order Laguerre– as well as Ince–Gaussian modes, being well-studied tools in optical manipulation, we demonstrate for the first time to our knowledge the development of sophisticated SFD configurations. We show shaping the flow field and controlling the type, number, spatial location and order of formed singular points in these TEFs. Our approach facilitates on-demand sculpting energy flow fields and their complex topologies for future applications in, for example, optical manipulation based on tailored polarization structures.

Fully-structured light is an emerging approach to sculpt light in all its degrees of freedom, i.e. amplitude, phase and polarization with a high transverse resolution and complex modulation patterns. Such an attractive and versatile approach for advanced optical trapping or fabricating novel materials still poses fundamental as well as technical challenges. Though the implementation of spatial light modulators (SLMs) has opened up a promising path for this task, up to now, fully-structured light can only be achieved using interferometric methods, multiple SLMs, or split-screen techniques reducing spatial resolution. We present a sophisticated single-beam approach based on spatial multiplexing, which does not only allow joint customization of phase and polarization combined with natural and prospectively even on-demand amplitude modulation, but also ensures high spatial resolution by the use of a single standard SLM in the full-screen mode. We demonstrate the capabilities of our approach realizing double phase modulated light fields, as well as first- and higher-order vector modes with additional global phase modulation and natural amplitude shaping. These findings open new perspectives to optically trap polarization-sensitive, i.e. magnetic particles and advance laser material machining in anisotropic, birefingent matter.

In this study, we present a bonding technique for fabricating microfluidic devices with surfactant-added SU-8 (hydrophilic SU-8) as the structure. The technique is based on an adhesive wafer bonding process. The hydrophilic SU-8 plays the roles of both an adhesive layer (glue) as well as a structural layer. Due to its special feature, bonding with hydrophilic SU-8 could be conducted without pressurizing equipment. The material could define structure satisfactorily and it has a hydrophilic surface in a cured state, and has a good adhesion capability with various substrates (glass, silicon or PDMS) after oxygen plasma treatment. The performance of the material was verified by using the Raman spectroscopy to analyze the possible changes in chemical structure, measuring contact angle to characterize hydrophilicity and several tests to confirm the bonding capability. The effect of different parameters on the bonding has also been explored. 2D (one-layer hydrophilic SU-8) and 3D (two-layer hydrophilic SU-8) sandwich configurations were constructed using this bonding technique. The tests showed the bonding strength to be in the range of 2–14 kg cm−2 measured by the pull test, and the microchannels could stand up to 0.4 atm pressure drop in the hydrodynamic testing. The present material has good properties in bonding, and the procedure is fast, compatible and easily implementable with a standard photolithography. It is suitable for microstructure and microelectronics integration, and highly involved three-dimensional (3D) microstructures.

We investigate the characteristics of correlation signals accomplished by content addressing in a phase encoded volume holographic storage system under different realistic conditions. In particular, we explore two crucial cases with respect to the structure of the data. The first one deals with a scenario where only partial or defective data are available for content addressing. The second case takes similarities among the stored data sets into account, which significantly differ from their statistical correlation. For both the cases we provide, for the first time, a theoretical approach and present experimental results when employing phase-code multiplexing. Finally, we discuss the reliability of the employed methods.

A time-dependent model for the formation of self-trapped optical beams in photorefractive media by counterpropagating laser beams is analysed. It is shown that dynamically the beams may form stable steady-state structures or display periodic and irregular temporal behaviour. Steady-state solutions of non-uniform cross section are found, representing a general class of self-trapped waveguides, that include counterpropagating spatial vector solitons as a particular case. Two critical curves are identified in the plane of parameters, the first one separating vector solitons from the stable bidirectional waveguides and the second one separating stable waveguides from the unstable ones. Dynamically stable rotating beam structures are discovered that have no analogues in the usual steady-state theory of spatial solitons.

Large two-dimensional spatial soliton arrays are generated experimentally and numerically in photorefractive media and their waveguiding properties at red and infrared wavelengths are demonstrated. An enhanced stability of solitonic lattices is achieved by exploiting the anisotropy of coherent soliton interaction and by controlling the relative phase between soliton rows. Manipulation of individual solitonic channels is accomplished by the use of separate control beams.

We investigate the durability of volume holograms in bismuth tellurite crystals, Bi2TeO5. This material enables self-fixing of holograms during the recording process rendering any further fixing technique unnecessary. Therefore the material overcomes the vulnerability of holograms which is a typical inconvenient property of inorganic storage crystals. The quality reduction of reconstructed analogue and digital data pages under permanent read-out is studied. In terms of digital page-oriented storage, the change of the bit error rate is investigated. For comparison, all experiments are also performed on iron doped lithium niobate crystals, LiNbO3:Fe.

We report on the stable self-focusing of light for various degrees of spatial coherence. Since the diffraction of a partially spatial coherent light beam is mainly governed by the transverse correlation width, its self-focusing is generally non-trivial. Here, we systematically demonstrate that partially coherent solitons can be generated in a non-instantaneous nonlinear material when the external parameters are properly adapted to the degree of coherence of the light beam.

A photorefractive two-beam-coupling based novelty filter is sensitive to amplitude and phase changes. However, the phase sensitivity of this device has remained unexploited until now. In this paper we develop and demonstrate a method to overcome the effects of contour formation in novelty filter output and consequently employ the novelty filter as a quantitative real-time transient phase-measuring instrument. A microscope based on a two-beam-coupling novelty filter is implemented and is used for detecting as well as measuring phase changes introduced by moving homogeneous phase objects. The two-dimensional output from the microscope is analysed, and a method based on the intensity dependence of the photorefractive time constant is proposed to overcome the effects of contour formation in the context of real-time transient phase measurement. The phase transfer function of the novelty filter system is experimentally determined and a phase measurement resolution of at least λ/20 at 532 nm is achieved.

We show that manipulation and selection of optical patterns is possible by detuning the frequency of one of the two waves in counterpropagating photorefractive two-wave mixing with a feedback mirror. An analytical expression for the onset of modulational instability is derived for the general case of an arbitrary complex coupling constant, including a possible frequency shift of the generated sidebands. The influence of frequency detuning of the pump beams on the spatial scale of the resulting pattern and on the threshold value of the photorefractive coupling strength for modulational instability is investigated. The spatial scale and the frequency detuning of the generated sidebands were measured in an experiment using a photorefractive KNbO3 crystal. Comparison of theory and experiment show agreement for positive frequency detuning of the pump beams. For negative detuning we observe clamping of the spatial scale and no frequency shift of the sidebands. Possible explanations of this deviation between analytical results and experiment are discussed.

Higher-order polarization singularities embedded in tailored vector beams are introduced and experimentally realized. As holographic modulation allows to define order and location of any vectorial singularity, the surrounding vector field can be dynamically shaped. We demonstrate light fields associated with flowers or spider webs due to regular and even irregular patterns of the orientation of polarization ellipses. Beyond that, not yet investigated hybrid structures are introduced that allow generating networks of flowers and webs in very close vicinity. Our results pave the way to applications of singular optics in spatially extended, optimized optical tweezing and high-resolution imaging.

We report on the experimental observation of spatially oscillating solitons in two-dimensional nonlinear photonic lattices, realized by optical induction using a continuous nondiffracting Weber beam. Thereby, we introduce and demonstrate a new type of transverse soliton dynamics originating from the unique parabolic geometry of the photonic lattice. First, we numerically calculate the fundamental soliton solution for this lattice and experimentally demonstrate its existence. Afterwards, we experimentally launch the soliton with an additional transverse momentum and observe harmonic spatial oscillation during propagation.

The positive magnetoconductivity Delta sigma (B) of InP near the metal-insulator transition (MIT) was measured as a function of the conduction electron concentration and the compensation ratio. Starting deep within the metallic regime the charge carrier density of the sample was reduced stepwise below the critical value of the MIT by fast neutron irradiation due to the acceptor-like nature of the irradiation defects. Up to being exposed to a fast neutron dose of phi tf=1.4*1016 cm-2 the sample behaved in a metallic fashion, and subsequent to each irradiation step the inelastic scattering time was deduced from the slope of the Delta sigma =f(B2) curves in the temperature range 2 K

We report on the existence and properties of vortex solitons at the edge and in the corner of two-dimensional triangular photonic lattices. We describe novel types of discrete vortex solitons, as well as the ring surface vortex solitons, localized in the lattice corners or at its edges. We observe that stable surface vortex solitons exist only in the form of a discrete six-lobe solution at the edge of the photonic lattice. Oscillations and irregular dynamics are observed for the ring vortex solutions and discrete two- and three-lobe solutions.

We study Anderson localization of light in one-dimensional (1D) and 2D photonic lattices. The influence of nonlinearity and disorder on Anderson localization in both systems is studied numerically. A sharp difference between localization in the linear and the nonlinear regimes is observed. Localization in the linear regime is more pronounced in the 2D lattice than in the 1D lattice. In the nonlinear regime, the coexistence of nonlinearity and disorder leads us to different conclusions. There are different nonlinear regimes in which 1D localization is more pronounced than 2D localization.